Currently, the most common method of temporarily occluding the ascending aorta and arresting the heart during open-heart surgery utilizes a mechanical cross clamp and a cardioplegia cannula. Once the chest cavity has been opened, access to the heart and to the adjacent vessels is provided. The ascending aorta is partially dissected from the surrounding tissue and exposed. Arterial and venous cannulas are inserted and sutured into place. The cannulas are connected to the cardiopulmonary bypass machine, and bypass blood oxygenation is established.
At this point, the heart must be arrested and isolated from the rest of the circulatory system. A mechanical cross clamp is positioned between the cardioplegia cannula and the aortic cannula and is actuated. The aorta is completely collapsed at the clamp site, thus stopping flow of blood between the coronary arteries and the innominate artery, and the oxygenated bypass blood is shunted around the heart. Once the vessel occlusion has been completed, cardioplegia solution is introduced through the cardioplegia cannula to arrest the heart. The surgeon may now proceed with the desired operation.
Other less common means of occluding the aorta include percutaneous balloon catheter occlusion, direct aortic balloon catheter (Foley) occlusion, aortic balloon catheter occlusion, and an inflating diaphragm occluder (Hill--occlusion trocar). The percutaneous balloon catheter is inserted typically from the femoral artery feed through the descending aorta, across the aortic arch into position in the ascending aorta. Once in the ascending aorta, the balloon occluder is inflated and flow stopped.
As a simple replacement for the mechanical cross clamp, a Foley catheter may be placed through an additional incision site near the standard cross clamp site. Once inserted, the Foley catheter balloon is inflated and flow is stopped. Similarly, an aortic balloon catheter is placed directly into the aorta. This catheter replaces the standard aortic cannula by delivering the cardiopulmonary bypass (CPB) blood back to the arterial circulatory system. The occluder balloon is located on the catheter proximal to CPB blood exit port on the cannula. The occlusion trocar is desired to offer similar features as the aortic balloon occluder cannula and would be used in place of the standard aortic cannula. However, it relies on an inflatable diaphragm to occlude the vessel.
The use of a balloon to occlude an artery has been disclosed by Gabbay, U.S. Pat. No. 5,330,451 (this and all other references cited herein are expressly incorporated by reference as if fully set forth in their entirety herein). The Gabbay device included a perfusion cannula having a proximal balloon occluder and a distal intra--aortic balloon to divert blood to the carotid arteries. The Gabbay perfusion cannula is disclosed for use during open-heart surgery in order to prevent complications associated therewith.
Moreover, Peters, U.S. Pat. No. 5,433,700, discusses a method for inducing cardioplegic arrest using an arterial balloon catheter to occlude the ascending aorta. The Peters method includes the steps of maintaining systemic circulation using peripheral cardiopulmonary bypass, venting the left side of the heart, and introducing a cardioplegic agent into the coronary circulation. This procedure is said to prepare the heart for a variety of surgical procedures. Disclosures of similar endovascular occlusion catheters can be found in Machold et al., U.S. Pat. No. 5,458,574, Stevens, International Application No. PCT/US93/12323, Stevens et al., International Application No. PCT/US94/12986, Nasu, U.S. Pat. No. 5,425,708 and Grinfeld et al., U.S. Pat. No. 5,312,344.
Each of the existing methods of blocking aortic blood flow and arresting the heart carries with it some undesired aspects. The mechanical cross clamp offers simplicity and reliably consistent operation. However, the physical clamping action on the vessel has been linked to many adverse body responses. Barbut et al. ("Cerebral Emboli Detected During Bypass Surgery Are Associated With Clamp Removal," Stroke, 25(12):2398-2402 (1994), incorporated herein by reference in its entirety) noted the majority of embolic events (release) is associated with the actuation and release of the cross clamp during coronary bypass graft surgery. The clamping action may be responsible for breaking up and freeing atherosclerotic buildup on the vessel walls. In addition, the potential for vascular damage, like aortic dissections, may also incur during the clamp application.
The percutaneous balloon catheter occluder has a distinct drawback in that it must be placed with visionary assistance. Fluoroscopy is typically used to position the device in the aorta. This added equipment is not always readily available in the surgical suite. In addition, the catheter placement up to the aorta may also create additional vascular trauma and emboli generation.
The use of a Foley catheter to occlude the aorta requires an additional incision site to place the device. The extra cut is an additional insult site and requires sutures to close. Generation of emboli and the potential of aortic dissection directly associated with just the incision may potentially outweigh the benefits of using the catheter.
The aortic balloon occluder cannula addresses many of the deficiencies of the previous devices. Placement is easy to visualize, no extra cuts are required, and there is no need for the potentially traumatic cross clamp. However the currently--available aortic balloon occluders suffer from problems of migration within the ascending aorta because the cannulas on which the balloons are mounted are typically flexible tubes as disclosed by Grinfeld et al. and Nasu. Attempts to solve the migration problem include balloon designs with a large "footprint" in the distal region of the cannula. (See Nasu, supra.) This large footprint balloon is a less than adequate solution because it encroaches into the already limited area of the ascending aorta in which surgical access is available. Further, use of each of these aortic occluding balloons requires a cardioplegia cannula to be inserted through an additional incision site to arrest the heart.
A need exists for an aortic cannula having both a balloon occluder which can isolate the ascending aorta from peripheral vasculature without substantial migration of the occluder into the ascending aorta, thereby reducing or eliminating the need for aortic cross--clamping, and an associated cardioplegia infusion port which eliminates the need for a separate incision for a cardioplegia cannula. Existing devices are inadequate for this purpose.